Water, waterkringloop en klimaatverandering

We use water every day. That makes it seem very simple. But water is a special substance. For example, without water, life is not possible. And it is the only substance that occurs in all three phases in nature. Solid, liquid and gaseous. The melting point of ice is at 0° C. At that temperature, ice slowly turns into water. The boiling point of water is 100° C. Water then changes into water vapour. Water has some unique properties: Many substances dissolve well in water; take for example sugar or salt. This is often useful, for example if you drink tea with sugar. But it also makes water easily contaminated.

All the water in the world is part of the water cycle: The sun heats up the sea water. Part of the water evaporates and rises. High in the air, the water vapor cools. Small droplets form. These are clouds. The cold air further cools the water vapor. Due to this process of condensation, the droplets become larger and heavier until the cloud can no longer hold the droplets. Then it will rain. Part of the clouds rain empty above the sea. Another part of the clouds is blown to the land via air currents and rains empty there. The precipitation above land eventually returns to the sea via rivers or groundwater. About 70% of the Earth is covered with water. The water on Earth plays a major role in regulating temperature. For example, the oceans absorb large amounts of heat from the sun and gradually release it back into the atmosphere. This avoids extremes in heat and cold. The Earth’s climate is determined by wind and sea currents such as the warm and cold Gulf Stream. Due to global warming, changes are occurring, resulting in a different weather pattern worldwide. In some places it will be much too dry, while in other places it will be much too wet.

Some people still think climate change is hype. In a way that is not surprising because climate change is difficult to feel. You won’t notice much difference from year to year. But you can measure it. Since 1880, the temperature on Earth has been tracked. As a result, we know that the Earth is getting warmer. Global warming is caused by an increase in greenhouse gases in the atmosphere, such as CO2 and methane. These gases trap the heat from the sun. So: the more greenhouse gases, the warmer it gets on earth. Trees and plants can neutralize greenhouse gases by absorbing them and converting them into oxygen. This cools the earth. Due to large-scale deforestation and continuous greenhouse gas emissions, this is becoming increasingly difficult. We are seeing the consequences of this more and more clearly.

The changing climate causes flooding in the Netherlands in three ways: 1. Rising sea level The rise in sea level is due to the expansion of seawater, the melting of glaciers and small ice caps, and the steady shrinking of the large ice caps in Greenland and Antarctica. The sea level rise off the Dutch coast is largely due to the South Pole. By the way, did you know that melting ice in the North Pole does not contribute to sea level rise? The ice of the North Pole floats on the sea. When it melts, the volume of ice decreases, but the volume of water that replaces it is exactly the same. Oceans and ice sheets respond very slowly to changes in the atmosphere. Even if temperatures stop rising after 2100, sea level rise will continue for centuries. Even if the amount of greenhouse gases in the atmosphere remains limited. In the twentieth century, the sea level has risen about 20 centimeters. According to the Intergovernmental Panel on Climate Change (IPCC), sea levels have risen by 26 to 82 centimeters on a global scale by the end of the 21st century. Satellite measurements show that the sea level is not rising at the same rate everywhere on earth. The sea level rise along the Dutch coast was almost as strong as the global rise in the past century. 2. Downpours We often have to deal with downpours in our country. The amount of rain in the summer months does not increase that much, but it falls in peaks. In such a downpour, so much water falls in a short time that the sewers and ponds in the residential area cannot store it. The water remains in the street, or worse, it flows into the basements of homes. In lesson 4 we will discuss the measures we are taking to prevent flooding in the streets. 3. Water via the river More water enters our country via the major rivers. Due to meltwater and downpours in Germany, France and Belgium, the excess water is discharged in peaks via the Dutch rivers. In 1993 and 1995 this led to extremely high water levels in Limburg, with the threat of flooding. This was the reason to start the ‘Room for the River’ project. Space for water storage has been created at the major rivers. In some places the river has been widened and in other places temporary storage areas have been set up. In lesson 5 we will take a closer look at the measures that are being taken to protect the Netherlands against the water.

The effects of climate change are felt all over the world. For example, in 2014, Central America experienced its worst drought on record, while South America experienced flooding. People died in both regions, crops failed and it took several years for the affected areas to recover from the disaster. In lesson 7 you will learn more about the consequences of climate change for people and their living environment.